紅菜坪地區位於台灣中部南投縣中寮鄉樟平溪上游之永祿溪南岸，紅菜坪地滑引發於1999年9月20日(UTC)集集大地震(Mw=7.6)。本研究選用地化方法: 同位素及水化學結合地形及地質調查建立地化特徵與臺灣南投紅菜坪地滑之關聯。於2008年5月至2009年5月進行月採樣，水樣包含溪流、池塘、地下水、滲水及永祿溪溪水並分析各樣品之氫氧同位素、特定離子濃度、電導度及pH值。由水文地化分析結果顯示降雨補注或水土平衡不能完全解釋地下水的化學特性，各個水體間的相關性可藉由水化學及同位素組成隨時間、空間之變化來解釋；中至上邊坡的水體型態為Ca/Mg-HCO3-、下邊坡則為Na-HCO3-且水體含有非預期性高的硫酸根離子，且濃度隨著高程增加而遞減。綜合水文地化特徵及剖面資料分別建立流場概念模式以探討之水來源及流徑。 Hungtsaiping is located at the south bank of the Yonglu stream (the upper stream of Jhangping Stream), Chungliao Village of Nantou County, central Taiwan. Occurring on September 20, 1999 UTC, Hungtsaiping landslide was triggered by the Chi-Chi earthquake (Mw=7.6) which occurred near the town of Chi-Chi in Nantou County, central Taiwan. Coping with the geological and geomorphologic investigations, this study makes an attempt to find the relation between geochemical characteristics and landslide in Hungtsaiping area. Geochemical methods including isotope and hydrochemistry were used in this study. Water sampling was carried out from May 2008 to May 2009. Water samples were collected from spring waters, creeks, ponds, groundwater and the Yonglu stream once every month during the studying period. Oxygen and hydrogen stable isotope, ionic concentrations, as well as electrical conductivity and pH value were analyzed. The relationship between geochemical characteristics and landslide can then be evaluated. Analytic results indicate that calcium and magnesium bicarbonate-rich water was found on the top and the middle part of the slope. On the other hand, sodium bicarbonate-rich water as well as exceptionally high sulfate concentration was found on the foot of the slope, the sulfate content decreased with increasing elevations until the middle part of slope. A conceptual model of flow process and water origin in Hungtsaiping landslide was established by summarizing the features of hydrogeochemical analyses and the profiles in this study.
